This invention relates in general to wheel mountings and more particularly to a mounting for the road wheel of an automotive vehicle.
The nondriven road wheels of many automotive vehicles rotate about spindles that are fixed in the sense that they do not rotate—although they may pivot for steering. Typically, a nondriven wheel on such a vehicle is attached to a hub which rotates about a spindle on a pair of antifriction bearings. The two bearings have rolling elements which roll along raceways that are angled with respect to the axis, so that one bearing takes thrust in one axial direction and the other in the opposite axial direction. Of course both transfer radial loads. Being mounted in opposition, the bearings lend themselves to adjustment between settings of endplay and preload. Typically, the setting is controlled with a nut that threads over the spindle and against the inner race for the outboard bearing, so that the nut controls the spacing between the inner races, often referred to as “cones”, which are carried by the spindle. In endplay radial clearances exist with the bearings, and their presence reduces friction, but it may also induce wheel wobble which detracts from the stability of the vehicle and damages the inboard seal that protects the bearings. Prelaod on the other hand, eliminates wobble and thus improves stability, but preload increases friction. Too much preload can damage the bearings and produce excessive frictional losses. Ideally, the bearings should operate with a light preload.
Procedures currently utilized for setting wheel bearings lack precision. Often the setting is determined by the torque applied to the spindle nut or by monitoring the torque required to rotate the wheel that the bearings support. Both procedures can produce errors of significant magnitude. Aside from that, the nut is secured against rotation by a cotter pin which positions the nut only at in limited angular increments and thus further detracts from the precision desired for setting high performance bearings.
Finally, the bearings require seals between the hub and spindle to retain a lubricant within the interior of the hub and at the bearings and to exclude containments from the bearings. These seals possess contact lips which bear against the spindle and create drag.
Some high performance wheel bearings, such as those used on race cars, must operate with a minimum of friction and a high measure of stability. Conventional bearings for automotive wheel mountings do not possess these characteristics to the extent desired.